The present invention relates to manually powered devices. More specifically, the present invention relates to the effective generation, conversion and utilization of electrical energy generated by manually powered mechanisms.
Portable electronic devices, radios, lights, toys, electronic remote controls and/or wireless electronic remote controls, can be powered by portable power sources, such as batteries which store chemical energy, springs which store mechanical energy or by input of manual energy directly converted to electricity. Batteries convert the stored chemical energy into electrical energy when under load. Stored mechanical energy and direct mechanical energy are converted into electrical energy by a generator, commonly characterized by the use of a DC motor with coils on the rotor and ferrite permanent magnets on the stator. Such devices have the advantage of being portable, usable in remote locations, and are not dependent on connection to an external power source.
When a spring system wound by manual input of energy is used as the sole energy source in a portable device, the maximum play time is limited to the time the spring is unwinding. The spring must be rewound to continue use of the device.
Spring storage power systems typically used in personally powered devices waste some of the energy stored in the spring. Present power systems provide a constant voltage, which wastes power at low power usage levels and causes clipping at high power usage levels. The power system dumps the excess energy whenever the output current of the generator exceeds the instantaneous need of the device, thereby not making use of some of the energy stored in the spring.
In a typical application of a spring motor, it is convenient to release the spring tension at a constant angular rate. When the spring is coupled to a generator with fixed gear ratio, a constant angular rate of unwind corresponds to constant voltage output of the generator. However, the output torque of a two-spool spring motor is not constant but decreases as the spring unwinds. As a result the power output, which equals torque multiplied by angular frequency, is not constant. In the case where the spring motor is connected to an electrical generator to run some electric device, it is undesirable to provide diminishing power. As the electrical load typically requires a minimum power level to operate, the spring motor has to be oversized so that the last turns of the spring wound motor provide the minimum torque required. At all other times the excess torque leads to excess power which is not used by the electrical apparatus.